Pratt through truss. The Bridge Street Bridge in Portland is a rare two-span metal through truss, with two spans 100 feet in length, featuring decorative treatment at the end posts. This is the oldest known surviving example of a truss bridge built in Michigan by the Groton Bridge and Manufacturing Company of Groton, New York, a significant Eastern bridge manufacturing firm. It was listed as eligible for the National Register of Historic Places in April, 1986.

Editor's Note: The NRHP list shows the Bridge Street Bridge added to the list in 1980.